1. Field of the Invention:
This invention relates to a resin molding die having the function of a gate cutter. More particularly, this invention relates to a resin molding die capable of automatically cutting off a gate slug from a molded article before a mold opens.
2. Description of the Prior Art:
A molded article producted by injection molding in which molten resin is injected into a mold cavity through a gate has integrally a gate slug formed inevitably at the gate in the mold. The gate slug formed integrally on the molded article has generally been cut off by use of a hand tool such as a nipper after the molded article is released from the mold upon completion of an injection molding shot. The work of cutting off the gate slug from the molded article requires labor and proves to be troublesome. Furthermore, the gate slug cannot be finely cut off, thereby to deteriorate the quality of the molded product.
Japanese Patent Application Public Disclosure No. SHO 60-264217(A) proposes a method in which a gate slug formed on a molded article is cut off by means of an ejector pin at the time when a mold is open.
Otherwise, a structure in which a cutter which moves transversely along the parting line between molding die halves so as to cut a gate slug off from a molded product has been proposed in Japanese Patent Application Public Disclosure No. SHO 60-68922(A).
The former method for cutting off the gate slug is effected by ejecting the ejector pin to release the molded product from the mold in a mold opening process. However, it is impossible to automatically cut off the gate slug. This is because the molded product which is still retained in one molding die half provided with the ejector pin is not supported by the other molding die half at the time the molding die halves are open, and thus, no means supports the molded product when the ejector pin is ejected to release the molded product from the mold. Therefore, this prior art method has entailed a disadvantage that it can be applied merely to a specific molding die structure.
The latter gate slug-cutting structure necessitates a large-scaled and complicated mechanism for sliding the cutter along the parting face of one molding die half. Since the gate slug-cutting in either technique is carried out after the molding die halves are open, both the conventional slug-cutting techniques cannot be adapted to speeding up of injection molding. That is to say, the work of cutting off the gate slug according to the former slug-cutting method consumes much time because the ejector pin is ejected after a mold opening process is completed. Also, the latter will increase the time required for moving the cutter across the gate position in the parting face of one molding die half after the molding die halves are complately open.